The invention relates to combustion of slurry fuel, particularly to the combustion of liquid-coal slurry fuels, and more particularly to a device by which is obtained flash evaporation of the liquid in a slurry fuel thereby aiding the ignition and combustion of the fuel.
Pulverized coal is widely used as a fuel for boilers and furnaces. Also, engines, such as the diesel and gas turbine types, have been designed for using pulverized coal, but have not been developed sufficiently for commercial utilization. For a brief review of the prior efforts relative to the development of engines using coal as a fuel, attention is directed to a paper LBL-16622 entitled "Coal-Fuel Diesel Engines", F. Robben, presented at the Society of Automotive Engineers Fuels and Lubricants Meeting, San Francisco, Calif., Oct. 31-Nov. 4, 1983.
As the result of increased fuel consumption and the current oil reserve, there has recently been a renewed interest in the use of coal, particularly due to the increasing cost of oil and the existence of large coal reserves in the United States. A major problem associated with the increased use of coal, especially for smaller installations, is the cost of the delivery of coal and the cost and complexity for coal handling and crushing equipment.
Efforts to resolve the above problem, include the preparation and delivery of pulverized coal in the form of a liquid slurry (coal-water), which are being rapidly developed and promise a cost-effective, safe and environmentally sound method for coal transportation, storage and distribution. A coal refining industry is arising that will clean the coal of undesirable foreign matter and will pulverize, prepare and treat the coal-water slurry to achieve desirable liquid, storage and combustion properties. The most immediate application is for conversion of oil and gas boilers and furnaces to coal slurry fuel, but substantial efforts are underway for development of engines, such as diesel and gas turbine, for using a coal slurry fuel.
Two problems are associated with the combustion of coal slurry (coal-water) fuels. These problems are delayed ignition, due to the energy needed to evaporate the water, and the agglomeration of small coal particles into larger particles during the combustion process. Both problems were anticipated and have been demonstrated in various combustion tests and other experiments. Thus, a need has existed for methods or means of resolving these two problems.
Therefore, it is an object of this invention to reduce the magnitude of the problems associated with combustion of coal-liquid slurry fuels by improving atomization and minimizing energy required for ignition.
A further object of the invention is to at least reduce the magnitude of the coal-water slurry fuel combustion problems (e.g. ignition delay) by preheating the slurry to reduce ignition energy, and by improving the atomization so that each spray droplet contains few coal particles.
Another object of the invention is to provide a method and apparatus which produces flash evaporation of the liquid in a liquid-coal slurry fuel thereby aiding in ignition and combustion of the fuel.
Another object of the invention is to provide means for accelerating the ignition and combustion rates of water-coal fuel and for reducing the size of the ash particles formed from the coal.
Another object of the invention is to provide a method and means for preventing delayed ignition of a water-coal slurry fuel and reducing agglomeration of coal particles in the fuel.
Other objects of the invention will become readily apparent from the following description and accompanying drawings.